Apparatus of this kind are known to the art, and are based on the transmission of acoustic signals from three ground-located antennae which face in mutually different directions. It is known to position two of the antennae so that their centre axes, or the lines along which the sound waves are transmitted, form right angles with one another and are inclined at 60.degree. to the plane of the ground, while positioning the centre axis of the third antenna vertically. The received echo signals are measured with respect to transit time and the so-called Doppler shift between transmitted and received frequencies, and the results obtained thereby are converted by calculation to the magnitude and direction of wind components at that time.
It is also possible in this respect to evaluate or determine the measuring results obtained from different height levels, so as to produce mean values and standard deviations. This enables wind components at mutually different height layers to be established.
The measurement values obtained are processed and calculated in a micro-processor, in order to establish the speed and direction of the wind at selected heights.
These measuring systems available today are dimensioned to manage heights of from 50-500 meters, under favourable conditions. Each of the three antenna units used in the system, however, is two meters high and weighs 130 kg/unit, which means that they must be placed on a trailer, if the system is to be made mobile. In addition hereto, the trailer must always be pointed in one and the same direction, for example from north to south, in order for the established wind-speed values to be correctly related.